This invention pertains to a medical instrument. More particularly, this invention pertains to a medical instrument utilizable in endoscopic procedures. This invention also relates to an associated method.
Medical cauterization snares are essentially electrically energizable loops of wire. A cauterization snare is typically inserted in a collapsed configuration through the biopsy channel of an endoscope into a patient. Inside the patient, the cauterization snare is ejected from the endoscope biopsy channel and naturally expands to an opened configuration under the action of its own internal stresses. The snare is then manipulated from outside the patient and placed over a polyp or other tissue mass. The tubular member is then moved in the distal direction to close the loop about the base of the polyp or tissue mass. Then the cauterization loop is withdrawn in the proximal direction into the tubular member to sever the polyp. Electrical current is conducted through the loop provided that the instrument is connected to a voltage source and provided that the loop is in contact with the patient's tissues. Heat is generated in the loop by virtue of the electrical current conduction.
As disclosed in U.S. Pat. Nos. 5,201,740, 5,190,542, 5,486,182, and 5,759,187, a pouch may be attached to the cauterization snare for capturing a polyp or other tissue mass as it is severed from the patient's internal tissues. One advantage of this structure is that several polyps may be collected in succession during the withdrawal of an endoscope from a patient.
A common problem in endoscopic procedures is that polyps come in different sizes. If the snare used to harvest a polyp is too large, it is difficult to encircle the polyp with the cauterization loop. Other tissue structures within the patient obstruct the proper positioning of the snare about the polyp. In addition, upon placement of the snare about the polyp, the snare frequently does not optimally engage the polyp. For instance, only the two lateral sides of the snare might come into contact with the polyp, the far side of the polyp facing away from the endoscope, being spaced from the cauterization loop.
The conventional solution to the problem of different polyp sizes is to use snares of different sizes. However, this approach is cumbersome in that if a larger snare, for example, has been introduced to capture and ressect a large polyp, that snare needs to be first withdrawn from the biopsy channel only to be replaced by a small (mini) snare to capture a smaller polyp. This procedure is time consuming, and adds cost to the procedure because now two instruments instead of one need to be utilized.